Most proteins exhibit long-lived phosphorescence with lifetimes ranging from pi-sec to sec at room temperature in the absence of oxygen. Phosphorescence emission is exquisitely sensitive to environmental changes that occur on this time scale, as can be seen by the variability in lifetimes and ability to be quenched among proteins. How phosphorescence parameters are related to protein structure, dynamics and reactivity win be analyzed in the proposed research. Specific plans are to: 1. Correlate that observation of long-lived phosphorescence from tryptophan with the structure and composition of the protein. 2. Examine what determines the reactivity of excited triplet tryptophan with molecules external to the protein. 3. Study particular proteins in detail. The photochemistry of crystallins are of interest because they provide homologous proteins for study and they are very stable with high phosphorescence yield. The phosphorescence of cytochrome oxidase provides a spectroscopic parameter with which to examine the conformational changes that substrates and products induce on this complex protein.